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Optoisolator + Triac Question

  1. Jan 15, 2013 #1
    Hey guys I'd like to run a few things by you guys. I will be switching 120V 3A AC lines and am considering the following solution. I do not need synchronous switching by the way.

    This TRIAC
    http://www.digikey.com/product-detail/en/BT134-600E,127/568-5015-5-ND/1155119
    The datasheet says its rated up to 4A and has a max gate current of 2A.

    This Optoisolator
    http://www.digikey.com/product-detail/en/MOC3021/160-1374-5-ND/385844
    The datasheet lists the trigger current at about 15mA so I'll go with 20mA to be safe, and has a peak surge current of 1A.

    I will be triggering the optoisolator with 3.3V signals.

    So with these parameters I've gone with
    (3.3V - 1.3V) / .02A = 100 Ohms for the diode current limiting resistor on the optoisolator input.
    170Vpk / .95A ~= 180 Ohms for the gate current limiting resistor on the triac

    I will be using this schematic
    http://www.simpleio.com/design/triacout/images/TriacOut4Sch_L.gif [Broken]

    Does this all sound good?
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jan 15, 2013 #2
    To me the design looks good. The only thing I can think of is that if the load is at all inductive, you should have snubbers on the main triacs.
     
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